Ohtake H, Suyemitsu T, Koga M
Biochem J. 1983 Apr 1;211(1):109-18. doi: 10.1042/bj2110109.
Gel-filtration analysis of cytosol fraction obtained from unfertilized sea-urchin (Anthocidaris crassispina) eggs on Sephadex G-75 revealed the presence of two Zn-binding-protein fractions. The major Zn-binding protein fraction had a low molecular weight and a low absorbance at 280 nm, properties similar to those of the metallothionein found in the regenerating rat liver. These fractions were further purified by DEAE-cellulose and Sephadex G-50 chromatography. Homogeneity of the Zn-binding protein was judged by polyacrylamide-disc-gel electrophoresis and gel-permeation chromatography in the presence of 6 M-guanidinium chloride. The molecular weight determined by gel-permeation chromatography was 3900. This value is in good agreement with the minimum molecular weight calculated from the amino acid composition, which was 3655. Zn-binding protein is composed of 36 amino acid residues and the distinctive features include an extremely high content of cysteine, which accounted for one-third of the total amino acid residues, and a complete absence of aromatic amino acids, as well as of methionine, histidine and arginine. Zn-binding protein contained 4.1 g-atoms of zinc per mol and a trace of cadmium, but no copper, iron or calcium. The molar ratio of reactive thiol groups to metal ion was calculated to be 2.73:1. Possible roles of this Zn-binding protein in the homoeostasis of zinc in unfertilized sea-urchin eggs are discussed.
对从未受精的海胆（厚刺海胆）卵中获得的胞质溶胶部分进行葡聚糖凝胶过滤分析，结果显示存在两个锌结合蛋白部分。主要的锌结合蛋白部分分子量低，在280nm处吸光度低，这些特性与在再生大鼠肝脏中发现的金属硫蛋白相似。这些部分通过DEAE - 纤维素和葡聚糖凝胶G - 50柱色谱进一步纯化。锌结合蛋白的同质性通过聚丙烯酰胺圆盘凝胶电泳和在6M - 氯化胍存在下的凝胶渗透色谱法来判断。通过凝胶渗透色谱法测定的分子量为3900。该值与根据氨基酸组成计算出的最小分子量3655非常吻合。锌结合蛋白由36个氨基酸残基组成，其独特特征包括半胱氨酸含量极高，占总氨基酸残基的三分之一，完全不含芳香族氨基酸、蛋氨酸、组氨酸和精氨酸。锌结合蛋白每摩尔含有4.1克原子的锌和微量的镉，但不含铜、铁或钙。反应性巯基与金属离子的摩尔比经计算为2.73:1。本文讨论了这种锌结合蛋白在未受精海胆卵锌稳态中的可能作用。
